There has been proposed, for example, a catalyst containing palladium metal and another metal (lead, bismuth, thallium or the like) in Patent Document 1, as a palladium-containing catalyst for producing an α,β-unsaturated aldehyde and an α,β-unsaturated carboxylic acid through liquid-phase oxidation of an olefin with molecular oxygen.
Patent Document 1: Japanese Patent Application Laid-Open No. 56-59,722.